This invention relates to a unit fuel injector and a system therefor employed in association with a cylinder of an internal combustion engine. More particularly, this invention relates to a unit fuel injector and system therefor wherein a pump plunger and an injection valve are mounted in separate bores of a single housing adapted for mounting to the engine.
Many conventional fuel injection systems for internal combustion engines employ a single fuel injection pump for supplying fuel under high pressure to fuel injectors, each of which is associated with a cylinder of the engine. While many such fuel injection systems are highly efficient and provide a high level of performance over a wide range of operating conditions, a number of deficiencies are inherent in such systems. For example, the fuel line volume between the injection pump and the several injectors may vary resulting in a variation in the timing of the delivery of pressurized fuel to the different nozzles, particularly at relatively high speeds. Moreover, the high pressure fuel lines connecting the high pressure pumping chamber of the injection pump to each of the several injectors require fittings which are required to withstand high pressure. Such fittings are potential sources for the leakage of the pressurized fuel.
Unit fuel injectors wherein the high-pressure fuel is generated within or proximate the injector rather than at a remote high-pressure injection pump have been employed to overcome the previously described deficiencies and to incorporate other desired features. Prior art unit fuel injectors have employed a pump plunger which is coaxially mounted with respect to the injection plunger. However, substantial headroom is required by many such injectors in order to connect the rocker arm or actuating means of the engine with the end of the pumping plunger for actuation of the unit fuel injector. In addition to the difficulties of conforming to the headroom constraints of the engine, prior art unit fuel injectors generally have not incorporated efficient timing means to control the timing of injection of the fuel charge. The stroke control and timing control can be critical features at high engine speeds where relatively small quantities of fuel are required for each pumping stroke.